>If I want to put an auxiliary battery in my Subie-Westy, what would I need
>besides the battery and the dual battery relay kit like Bus Depot has?
I've
>saved a few posts on dual batteries, but not sure if anything else is
>required
Well you might want to get a
Low Voltage disconnect,( LVD)
 -cuts off dc to the devices when dc volts on batt drop below
   say 11v prevent complete discharge on batt,
lcd meter to show load/ chg rates
solar charge controller, for when you upgrade to a solar  panel
seperate dc panel for all the goodies on the 2nd battery

hey wait miniute this is just what I did so I found this quite compact
morning star 15M or 30M solar charge controller, with meters & lvd ~150-200
http://www.morningstarcorp.com/products/ProStar/index.shtml
ebay 172
http://cgi.ebay.com/ProStar-30M-MORNINGSTAR-Solar-CHARGE-CONTROLLER-w-METER_
W0QQitemZ6040387881QQcategoryZ41980QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

dc panel bussman model 15600 8-12 blade type fused ciruits
$12
http://www.bussmann.com/library/bifs/15600.PDF